The production of resin moldings of the type having conductive parts typically involves the use of high-conductive plastics. These high-conductive plastics contain, as a conductive filler, short metal fibers of copper, stainless steel or the like. For example, the Journal of the Plastic Molding Engineering Society of Japan (Molding, '93), pp. 143-144, describes a conductive resin composition containing a conductive filler of Pb--Sn solder powder (e.g., Pb: 70%, Sn: 30%). Also, Japanese Patent Publication (JP-B) 07-49491 describes a conductive resin composition containing a combination of conductive fibers and low melting point metal consisting essentially of Pb--Sn.
One general method for producing resin moldings having conductive parts is disclosed in Japanese Laid Open Patent Application (JP-A) 63-50482 and 01-207989. The method involves forming a primary molding for the backbone from a plastic molding material capable of being easily plated by chemical plating (i.e., an easily platable material), injecting a plastic molding material that is hardly platable by chemical plating (i.e., a hardly platable material) into the area of the outer surface of the primary molding that is not to be plated, and integrating these to produce a secondary molding. Thereafter, the exposed area of the easily platable material of the secondary molding is plated.
The conventional method of forming the conductive parts through plating is illustrated in FIG. 6. As illustrated therein, a filler and a base resin (for example, a thermoplastic resin) are first formulated in a predetermined ratio, kneaded and then pelletized into easily platable resin pellets (conductive material). Next, the resin pellets are formed into a primary molding to be the backbone through injection molding. The surface of this primary molding is etched and activated by catalytic treatment to facilitate the plating thereover. Next, the primary molding is subjected to secondary molding. Finally, the activated area of the surface is plated to form conductive parts. This method thereby produces a resin molding having conductive parts.
However, the conventional conductive composition comprising the conductive fibers and low melting point metal that consists essentially of Sn--Pb has a negative impact on the environment in that it contains lead, which is a harmful material. Substitutes for this material are presently needed.
In addition, the conventional method of producing resin moldings which have conductive parts requires an additional plating step for forming the conductive parts. This additional plating step undesirably increases the production costs associated with the method.